Event Title

Comparison of Grip Pressure between Pipe Wrench and Ergonomically Designed Wrench During Wrenching

Mentor 1

Dr. Naira Campbell-Kyureghyan

Location

Union Wisconsin Room

Start Date

24-4-2015 10:30 AM

End Date

24-4-2015 11:45 AM

Description

A pipe wrench (PW), the standard tool for gas utility workers, is used to change gas meters in both residential and commercial settings. Gas meters fittings require a large torque to tighten or loosen, resulting in a higher task difficulty and greater grip pressure on the worker. An ergonomically improved wrench with an interchangeable handle has been designed for gas meters to be used in place of pipe wrenches. The ergonomically designed wrench (EDW) is lighter, has an improved handle shape and length (dimensions), and a larger cross sectional area than a comparable 18 inch long PW. It is hypothesized that the change in shape, weight, and cross sectional area of the EDW will reduce the pressure on the user’s hand and reduce the required task efforts. Fourteen right handed male subjects inexperienced at using wrenches volunteered to participate in this study. Subjects were asked to loosen and tighten two fittings of a gas meter. Markings on the gas meter and the fitting were aligned to ensure the fittings were at the same torque for each trial. The gas meter was attached to a modular structure in order to alter the task height. The height of the fittings was 35’’ from the floor to simulate a common position of gas meters in the field. Subjects loosened and tightened fittings using both wrenches. The order of wrench was randomized per each subject. A 24 pressure sensor glove (FSA, Vista Medical) was placed on the subjects’ dominant hand to measure grip pressure. Sensors rested across the subjects’ palm and fingers excluding the finger tips. After collection, the sensors were separated into 7 zones across the hand for analysis purposes. The data was statistically analyzed and a student’s t-test was performed. Overall 56% less pressure was applied to the hand when comparing the EDW to the PW. Grip pressure consistently reduced across all zones, especially across the fingers, in both tightening and loosening tasks. Percent difference varied among the zones from 1-27%. The lowest percent difference was seen at the base of the fingers and the greatest differences were seen in the fingers and the lower region of the palm opposite the thumb during the loosening task. The pressure was reduced by 10%, 12%, and 27% respectively. Task time reduced consistently by about 10 seconds while using the EDW. Statistical analysis revealed a p-value of 0.05. The EDW handle was 8 inches longer than the PW, about 40% longer than the PW. In order to take this change in length into account while calculating results, PW data was projected using the length proportion to the EDW. Overall, there was less grip pressure when using the EDW compared to the pipe wrench. A few points can be drawn from these results. First, the shape and size of the EDW contributed to the reduction in grip pressure at any given hand zone by distributing the force over the larger area. Secondly, the longer handle of the EDW reduces the required force to generate an equivalent torque as for the standard PW. Finally, the reductions in task time lowered the overall effort of accomplishing the task, and resulted in less grip pressure on the user's hand.

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Apr 24th, 10:30 AM Apr 24th, 11:45 AM

Comparison of Grip Pressure between Pipe Wrench and Ergonomically Designed Wrench During Wrenching

Union Wisconsin Room

A pipe wrench (PW), the standard tool for gas utility workers, is used to change gas meters in both residential and commercial settings. Gas meters fittings require a large torque to tighten or loosen, resulting in a higher task difficulty and greater grip pressure on the worker. An ergonomically improved wrench with an interchangeable handle has been designed for gas meters to be used in place of pipe wrenches. The ergonomically designed wrench (EDW) is lighter, has an improved handle shape and length (dimensions), and a larger cross sectional area than a comparable 18 inch long PW. It is hypothesized that the change in shape, weight, and cross sectional area of the EDW will reduce the pressure on the user’s hand and reduce the required task efforts. Fourteen right handed male subjects inexperienced at using wrenches volunteered to participate in this study. Subjects were asked to loosen and tighten two fittings of a gas meter. Markings on the gas meter and the fitting were aligned to ensure the fittings were at the same torque for each trial. The gas meter was attached to a modular structure in order to alter the task height. The height of the fittings was 35’’ from the floor to simulate a common position of gas meters in the field. Subjects loosened and tightened fittings using both wrenches. The order of wrench was randomized per each subject. A 24 pressure sensor glove (FSA, Vista Medical) was placed on the subjects’ dominant hand to measure grip pressure. Sensors rested across the subjects’ palm and fingers excluding the finger tips. After collection, the sensors were separated into 7 zones across the hand for analysis purposes. The data was statistically analyzed and a student’s t-test was performed. Overall 56% less pressure was applied to the hand when comparing the EDW to the PW. Grip pressure consistently reduced across all zones, especially across the fingers, in both tightening and loosening tasks. Percent difference varied among the zones from 1-27%. The lowest percent difference was seen at the base of the fingers and the greatest differences were seen in the fingers and the lower region of the palm opposite the thumb during the loosening task. The pressure was reduced by 10%, 12%, and 27% respectively. Task time reduced consistently by about 10 seconds while using the EDW. Statistical analysis revealed a p-value of 0.05. The EDW handle was 8 inches longer than the PW, about 40% longer than the PW. In order to take this change in length into account while calculating results, PW data was projected using the length proportion to the EDW. Overall, there was less grip pressure when using the EDW compared to the pipe wrench. A few points can be drawn from these results. First, the shape and size of the EDW contributed to the reduction in grip pressure at any given hand zone by distributing the force over the larger area. Secondly, the longer handle of the EDW reduces the required force to generate an equivalent torque as for the standard PW. Finally, the reductions in task time lowered the overall effort of accomplishing the task, and resulted in less grip pressure on the user's hand.